Why do our tongues stick to metal in the winter?

This question addresses a dare—or to remain true to the movie, a "triple dog dare"—popularized in A Christmas Story: to stick your tongue to a pole in the winter. A tongue can stick to metal if the metal is below the freezing point of water, 32° Fahrenheit. This phenomenon occurs because the water on a tongue freezes when it touches a sub-32°F metal. Of course, if a metal is very cold, then a tongue will freeze to it more quickly.

The property which allows this rapid freezing to occur is thermal conductivity, or the ability of a material to conduct heat. Metal has considerably high thermal conductivity which means, in the case of the tongue-to-metal dare, it is able to absorb the heat of the tongue at a faster rate than the body is able to supply heat to the tongue. This high thermal conductivity is responsible for quickly cooling the water on a tongue to a temperature where it can freeze. Aside from metals, other materials of high thermal conductivity, like ice, can cause a similar freezing effect. In contrast, materials of low thermal conductivity would not be able to overcome the heat being supplied to the tongue, so the freezing effect would not occur.